Recipe 21.5. Handling Flash Remoting Responses

Problem

You want to retrieve a return value from a Flash Remoting method.

Solution

Use a Responder object with call( ).

Discussion

Recipe 21.1 discusses how to use the call( ) method of a NetConnection object to call a Flash Remoting method. The second parameter of that method is designed for specifying how Flash Player should handle responses. If you pass a value of null (as in the examples in that recipe), then no responses are handled. If you want to handle the responses, use a flash.net.Responder object.

The Responder constructor lets you pass it two function references, which handle return values and errors:

var responder:Responder = new Responder(onResult, onError);

When the result function gets called, it's passed one parameter with the value returned by the Flash Remoting method:

private function onResult(returnValue:Datatype):void {
}

The error handler method is passed an object with properties that describe the error in greater detail.

The following example makes a call to a Flash Remoting method called getAverages( ) and uses trace( ) to display the values. The getAverages( ) method returns an associative array with two properties called flash and actionscript:

package {
    import flash.net.NetConnection;
    import flash.net.Responder;

    public class Example {
        private var _connection:NetConnection;
        public function Example(  ) {
            _connection = new NetConnection(  );
            _connection.connect("http://www.rightactionscript.com/flashremoting/                gateway.php");
            var responder:Responder = new Responder(onResult, onError);
            _connection.call("FlashSurvey.getAverages", responder);
        }

        private function onResult(result:Object):void {
            trace(result.flash + " " + result.actionscript);
        }

        private function onError(error:Object):void {
            trace(error.description);
        }
    }
}

When returning values from Flash Remoting methods, you should always return types that serialize well; do not return record sets. Instead, you should always convert record sets to arrays of associative arrays. That ensures the greatest interoperability.